The present invention relates to a torque wrench and, more particularly, to an improved torque wrench which is non-jarring, has a variable limiting torque value and/or accommodates interchangeable output shafts.
Torque wrenches, come in a variety of different configurations--for example, the "T" shape wherein the longitudinal member is the output shaft and the transverse bar member is the handle, or the "L" shape wherein the longitudinal member is the output shaft and the half transverse bar member is the handle. However, all of these torque wrenches have in common the feature that manual torque applied to the handle is converted into a rotary motion of the output shaft, with the output torque not exceeding a predetermined value. Ideally, a torque wrench would have each of the following three features.
First, the torque wrench should be capable of driving a plurality of drive tips disposed at the free end of the output shaft. For example, different drive tips may be used for driving a male or female hex, Philips, flat blade, or any other drive configuration. This feature enhances the versatility and hence the value of the torque wrench since the same torque wrench may be used for a wide variety of applications require a torque wrench affording the same torque limit. To some degree this feature is found in particular prior art torque wrenches.
Second, the torque wrench should be capable of having the limiting torque applicable thereby changed in a simple, rapid and reliable manner. While most torque wrenches can have the value changed by modifying the structure of the handle so as to increase the spring or other biasing pressure, none of the prior art torque wrenches enable the limiting torque to be changed in a simple, rapid and reliable (predictable) manner without any change in the spring or biasing value. (Attempts to vary the spring or biasing means strength in order to change the limiting torque are subject to human error in setting the adjustment mechanism and thus may not reliably obtain the desired limiting torque limitation.) This feature also increases the versatility, and hence the value, of the torque wrench as the same torque wrench may be used in situations requiring a variety of different limiting torques.
Third, the torque wrench should be operable without the sharp jarring which characterizes the operation of a conventional torque wrench once the point of maximum or limiting torque has been reached. In a conventional torque wrench, the energy stored in the springs or other biasing means is released in the instant after the maximum torque is achieved. This results in a jarring effect on the screw, bolt, bit or other article being driven, as well as to the user's hand. This is especially important in medical applications where the jarring of the article into the patient can be extremely detrimental. None of the conventional torque wrenches have a non-jarring design wherein the cam, which delivers the preset maximum torque, is designed such that it resets after reaching the preset maximum torque without jarring the output shaft.
Accordingly, it is an object of the present invention to provide a torque wrench which, in one preferred embodiment, is of non-jarring design.
Another object is to provide a torque wrench which, in one preferred embodiment, is capable of having the limiting or maximum torque simply, rapidly and reliably changed.
A further object is to provide a torque wrench which, in one preferred embodiment, has interchangeable output shafts so that a different drive tip may be associated with different output shafts.
It is also an object of the present invention to provide a torque wrench which, in one preferred embodiment, incorporates at least two, and preferably each, of the above mentioned features.